The objective of this research proposal is: (1) to evaluate those factors responsible for normal in vivo platelet survival and determine the efficacy of platelets from random single donors versus matched single donors using Latham-bowl plateletpheresis; (2) to investigate those factors responsible for maintenance of in vitro platelet metabolic integrity and in vivo function after storage. Time, storage temperature, etc. will be evaluated for their effect on platelet ATP levels and in vitro metabolic activity, especially in relation to citric acid cycle enzymatic capacities. Multiple assays will be used to detect the presence of platelet isoantibodies, permitting the realistic evaluation of platelet transfusion therapy; (3) to evaluate the in vitro effect of patient's plasma on donor platelets' amino acid metabolism before and after alloimmunization and to compare the activities of citric acid cycle enzymes in platelets of leukemic patients before and after treatment.